Method for decomposing solid materials by explosive impacts



July 9, 1963 F. w. DE JAHN 3,097,089

METHOD FOR DECOMPOSING SOLID MATERIALS BY EXPLOSIVE IMPACTS Filed NOV. 22, 1960 Q I l F W I INVENTOR.

FREDRIK W. DEJAHN BY ATTORNEYS United States Patent This invention relates to the breaking down of sulfide ores such for example as pyrrhotite (FeS), nickeliferous pyrrhotite (FeS+l.5% Nil-0.4% Cu) calcopyrite (FeCuS molybdenite (M05) or zinc blende (ZnS). All of these ores are commonly concentrated by the floatation process and therefore will be in finely divided form and almost pure. My invention involves the concept that enough heat units are put into the ore to equal the heat of formation of the compound and to maintain the temperature of the surrounding atmosphere (which must be non-oxidizing) at a temperature above the vaporization point of sulfur (900 F. at normal pressure) and then the finely divided ore, while being fed forward preferably in a relatively thin layer (not over a few inches thick) is subjected to a series of rapid explosive shocks. At the same time there is a movement of the atmosphere countercurrent to the movement of the ore.

Under these conditions the bond of the sulfur to the metallic elements of the ore is broken and the sulfur tends to vaporize and is immediately carried off by the moving atmosphere. The remaining elements will pass onward in metallic state and can be separated and purified in any usual manner.

I find the best way of subjecting the ore to the shock treatment specified is to move it down an inclined plane in an enclosed passage and toward the bottom of the slope to fire explosive shots with great frequency into the passage. This can easily be done by using already developed machine gun mechanisms which fire blank cartridges of an appropriate high explosive which may for example be pentaerythritol tetranitrate (PETN) Actually I find PETN particularly useful for the purpose as its rapid rate of explosion gives the desired shock effect and it generates a relatively small volume of gas which is non-oxidizing. The relatively small amount of heat generated simplifies the firing mechanism.

This invention may be readily understood by reference to the accompanying drawing which illustrates the process as applied to the decomposition of calcopyrite, FeCuS The ore is heated in any desirable way to a temperature of about 900 F. and is introduced into an ore bin where it is flushed with nitrogen introduced through a pipe 12. This is to remove any free oxygen included in the ore. If preferred the ore may be flushed out before or during the heating step. In any event the hot ore free from the oxygen of the air is fed by a screw conveyor 14 and drops into the inclined reactor 16 where it slides down in a thin layer. Hot nitrogen gas is introduced near the bottom of the reactor through the pipe 18 and a mechanism similar to a water cooled machine gun is positioned as shown at 20 near the bottom of the reactor. This mechanism fires continuously into the reactor and for this purpose I use blank cartridges charged with PETN. If the ore is fed through the reactor at the rate of 330 tons of ore per day (24 hours) it is sufficient to use cartridges each containing 2 grams of PETN and which may be fired at the rate of about 400 per minute so that a total of about 300 lbs. of PETN per day is used.

The temperature in the reactor is maintained above the vapor temperature of sulfur and hot enough to supply the heat of decomposition and for this purpose about 10,000,000 cu. ft. per day of nitrogen is introduced through the pipe 18 which is heated to a temperature of approximately 1150 F. in a nitrogen heater 22.

Under the action of the heat and the impacts resulting from the explosions, the bond between the sulfur and the metal ingredients is broken and the sulfur is carried off by the flow of nitrogen and leaves the reactor by pipe 24, passing into the cyclone dust collector 2.6 at a temperature of about 910 The nitrogen and sulfur vapor then pass into the heat exchanger 28 where the vapors are cooled down to a temperature of approximately 250 F. and the precipitated sulfur vapors will pass into an electric precipitator '30 and are collected in the vessel 32. The residual nitrogen which has moved with the sulfur passes off from the vessel 62 into a gas holder 34. It may be noted that if the gas holder 34 is provided with a water seal this water seal may contain substantial percentages of ethylene glycol not only to prevent freezing but also to reduce the vapor tension of the water so low that very little water vapor will pass into the gas. The gas from the gas holder 34 under the action of a gas circulating pump 36 is in small part used for flushing out the ore bin which it enters through the pipe 12, and the major part passes through the heat exchanger 28 where it may be brought, for example, up to a temperature of 800 F. It then passes to the nitrogen heater 22 where it is heated with any desired type of fuel to a temperature of approximately 1100" F. Additional nitrogen as needed may be introduced through the pipe 38 and any excess may be bled out through the bin 10.

The reactor may have any desired cross section but a generally circular cross section is found to be satisfactory. It must have a flat bottom area over which the ore will slide. The exact angle of pitch of the reactor will vary with the ore employed and its fineness, but should be just enough so that under the agitation of the explosion the ore will move steadily downwardly but the speed of movement should be so related to the length of the reactor that it remains in the reactor for as much as 15 minutes or more.

Under the effect of the explosions the flowing ore will be in a continuous state of agitation and the metallic elements from which the sulfur has been separated will tend to go to the bottom leaving the undecomposed material on top of the flowing stream.

By the time the ore reaches the bottom of the reactor the sulfur is all driven out and the metallic elements pass into the discharge apparatus 40 and from that into a hopper 42. In the case of calcopyrite the metallic ingredients will consist of a mixture of copper powder and iron power and after being cooled under non-oxidizing conditions they may be separated as for example by a magnetic separator.

As previously stated this process is applicable to any of the sulfide ores. I have also found that the same type of apparatus can be employed for separating silica from metallic ores, as indicated in my earlier application Serial No. 44,553, filed July 22, 1960, of which the present application is a continuation-in-part. However, since in that case no sulfur is to be removed, the heating, and the use of nitrogen gas become unnecessary and it will be simply a case of subjecting the silica containing material to the action of the rapidly successive explosive charges as it moves downwardly through my apparatus. In like manner the apparatus may be used in any case where a flowing material is benefited by the effect of successive shocks.

What I claim is:

l. The method of decomposing metal sulfides which comprises the steps of flowing a thin layer of the metal sulfide in finely divided form through an enclosed area, the direction of flow being downwardly along a plane inclined at an angle less than to the vertical, supplying sufiicient heat to the metal sulfide within the enclosed area to at least equal the heat of formation of the metal sulfide and to raise the temperature thereof above the vaporization temperature of free sulfur, establishing a non-oxidizing atmosphere in the enclosed area, detonating pentaerythritol tetranitrate to generate in rapid succession a series of explosive shocks, and subjecting the thin layer of metal sulfide to the impact of the explosive shocks Within the enclosed area, thereby liberating free metal and free sulfur with the latter being substantially completely vaporized and expelled from the enclosed area.

2. The method of decomposing metal sulfides which comprises the steps of flowing a thin layer of the metal sulfide in finely divided form through an enclosed area, the direction of flow being downwardly along a plane inclined at an angle less than 90 to the vertical, supplying sufficient heat to the metal sulfide within the enclosed area to at least equal the heat of formation of the metal sulfide and to raise the temperature thereof above the vaporization temperature of free sulfur, moving a nonoxidizing atmosphere through the enclosed area in countercurrent flow to the flow of metal sulfide, detonating pentaerythritol tetranitrate to generate in rapid succession a series of explosive shocks, and subjecting the thin layer of metal sulfide to the impact of the explosive shocks within ,the enclosed area, thereby liberating free metal and free sulfur with the latter being substantially complete-ly vaporized and expelled from the enclosed area.

3. The method of decomposing metal sulfides which comprises the steps of flowing a thin layer of metal sulfide in finely divided form through an enclosed area, the direction of flow being downwardly along a plane inclined at an angle less than to the vertical, heating nitrogen gas to a temperature of about 1150 F., flowing the nitrogen gas through the enclosed area in countercurrent flow to the flow of metal sulfide at a rate sufficient to supply at least the heat of formation of the metal sulfide and to raise the temperature thereof to about 900 F., detonating pentaerythritol tetranitrate to generate in succession a series of explosive shocks at the rate of about 400 per minute, and subjecting the thin layer of metal sulfide to the impact of the explosive shocks within the enclosed area, thereby liberating free metal and free sulfur with the latter being substantially completely vaporized and expelled from the enclosed area.

References Cited in the file of this patent UNITED STATES PATENTS 1,555,078 Robertson Sept. 29, 1925 2,029,253 Walker Jan. 28, 1936 2,128,107 Tyrer Aug. 23, 1938 2,826,369 Haltmeier Mar. 11, 1958 2,859,952 La Tour et-al Nov. 11, 1958 2,965,474 Sargent et a1 Dec. 20, 1960 FOREIGN PATENTS 149,976 Australia Feb. 10, 1953 

1. THE METHOD OF DECOMPRISING METAL SULFIDED WHICH;; COMPRISES THE STEPS OF FLOWING A THIN LAYER OF THE METAL SULFIDE IN FINELY DIVIDED FORM THROUGH AN ENCLOSED AREA, THE DIRECTION OF FLOW BEING DOWNWARDLY ALONG A PLANE INCLINED AT AN ANGLE LESS THAN 90* TO THE VERTICAL, SUPPLYING SUFFICIENT HEAT TO THE METAL SULFIDE WITHIN THE ENCLOSED AREA TO AT LEAST EQUAL THE HEAT OF FORMATION OF THE META; SULFIDE AND TO RAISE THE TEMPERATURE THEEOF ABOVE THE VAPORIZATION TEMPERATURE OF FREE SULFUR, ESTABLISHING A NON-OXIDIZING ATMOSPHERE IN THE ENCLOSED AREA, DETONATING PENTAERYTHRITOL TETRANITRATE TO GENERATE IN RAPID SUCCESSION A SERIES OF EXPLOSIVE SHOCKS, AND SUBJECTING THE THIN LAYER OF METAL SULFIDE TO THE IMPACT OF THE EXPLOSIVE SHOCKS WITHIN THE ENCLOSED AREA, THEREBY LIBRATING FREE METAL AND FREE SULFUR WITH THE LATTER BEING SUBSTANTIALLY COMPLETELY VAPORIZED AND EXPELLELD FROM THE ENCLOSES AREA. 